Pressure sensor apparatus for measuring pressures including knock conditions in engine cylinders

ABSTRACT

Sensor apparatus for a multiple layer steel (MLS) cylinder head gasket measures combustion pressures for detecting engine conditions. A membrane is positioned at one end of an elongated metal tube, and the membrane end of the tube engages a cylinder bore boundary. A fiber optical sensor apparatus is fixed within the tube, and communicates with cyclic combustion events via the membrane. In one disclosed embodiment, optical wires from sensor apparatus situated at each engine bore are bundled into a common groove machined into an extended spacer layer radially outwardly of the conventional boundary of the gasket. The tube protects the sensor apparatus from damage of sealing stress on the gasket, and particularly at the bore perimeter. Each tube lies in a separate groove in the spacer layer that terminates at the bore boundary. A converter changes optical signals received from the apparatus into electrical signals for transmittal to a controller.

RELATED APPLICATIONS

This application claims priority under Title 35, USC Section 119(e) ofU.S. Patent Application No. 60/396,532 filed on Jul. 16, 2002 which isincorporated by reference in its entirety. This application also claimspriority under Title 35, USC Section 120 of U.S. patent application Ser.No. 10/077,411 (now U.S. Pat. No. 6,701,775), filed on Feb. 15, 2002, ofwhich the present application is a continuation-in-part, which isincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an apparatus embedded in andor applied to gasket structures, and more particularly to a sensingapparatus applied to combustion gaskets of internal combustion engines.More specifically, the invention relates to a pressure sensing apparatusprovided within structures of multi-layered steel combustion gaskets formeasuring pressure levels of combustion gases within the cylinder boresof internal combustion engines.

2. Description of the Prior Art

It is known to employ electronic sensors in gaskets for sealing betweenengine components including, for example, the block and cylinder head ofa multi-cylinder internal combustion engine. In one case, the gasketcomprises a sealing plate having several combustion chamber orifices,with combustion chamber sealing elements situated on the edges of thesealing plate surrounding the combustion chamber orifices. The gasketincludes sensor elements for cylinder-specific detection of sealingmovements perpendicular to the plane of the sealing plate, caused bypressure changes in respective combustion chambers being measured. Allof the sensor elements are arranged outside of the combustion chambersealing elements, and can be piezoelectric and piezoresistive, as wellas glass fiber light guide-style sensors.

In another example, a gasket enclosed sensor system is employed formeasurement of combustion chamber parameters and delivery of signals topoints external of the engine. The gasket includes a combustion openingsubstantially surrounding a combustion chamber, and includes an accessopening extending from the combustion chamber to a point external of theengine. A metallic sensor terminal is positioned within the accessopening, and insulating material substantially surrounds the metallicsensor terminal.

In yet another example, a fluid sensor and associated circuitry are usedto indicate presence of oil flow in a multi-cylinder internal combustionengine. The oil sensor includes a heating element positioned within theoil line, directly in the oil flow path. A comparator measures the valueof signals from upstream and downstream heat sensors, and triggers aswitching circuit when the temperature at the sensors approach oneanother to indicate an adequate oil flow to the engine.

In still another example, a gasket formed in the shape of an exhaustflange includes a load sensor comprising a pressure sensitiveelectrically resistive material positioned between electrodes andconductors extending outwardly of the perimeter of the gasket. A sealprovided between first and second layers of the gasket, and about theload sensor, provides a seal for the electrodes, which are positioned ina cavity to protect the sensor from fluids.

SUMMARY OF THE INVENTION

A sensor for a multiple layer steel (MLS) cylinder head gasket apertureboundary is adapted to measure combustion pressures occurring ininternal combustion engines for detection and control of engine knock,i.e. predetonation conditions, among other purposes. The structure ofthe sensor includes a pressure sensitive membrane at one end of a metaltube, wherein the tube is positioned adjacent a cylinder bore apertureboundary. The membrane is affixed to the tube at its aperture boundaryend, and an optical sensor structure is fixed within the tube downstreamof the membrane. The tube protects the optical sensor from becomingdamaged under high sealing stresses that occur at the cylinder bore. Asdisclosed, the sensor is placed into a spacer layer of the MLS gasket,in a groove formed in at least one spacer layer, and an optical fiberwire coupled with a sensor from each cylinder bore is bundled into acommon groove of the spacer layer. Various methods for forming thegroove are available. The groove may be located outside of theconventional component boundary of the gasket. Thus, the spacer layermay be extended radially outwardly of the conventional componentperimeter at the convenience of the gasket designer. Finally, aconverter is employed to change optical signals received from theoptical wire into electrical signals for appropriate transmittal to amicroprocessor of an engine control unit.

Where a plurality of cylinder bores is provided in the gasket, and tothe extent that pressure sensing is provided at each bore, a real timequality engine management control opportunity based uponcylinder-by-cylinder measurement of combustion pressure is provided. Thespecific cylinder-to-cylinder data can be input into an engine controlunit module that includes systems for optimization of engine performanceparameters, including fuel economy and emissions levels, among others.

As the pressure sensor apparatus is designed to be applied to aprotective tube positioned in a groove of a spacer layer, the apparatusmay be positioned between beaded or active layers of a multiple-layeredsteel gasket without severe risk of being crushed or overstressed.Various alternative embodiments for positioning the tube are disclosed.The sensor may also be positioned relatively close to the flame frontwithin the gasket structure, and as such can be particularly effectiveto measure pressure levels of cylinder-specific combustion gases in realtime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary plan view of one described embodiment of acylinder head gasket that incorporates the combustion pressure sensorsystem of the present invention, each sensor contained within aprotective cylindrical metal tube disposed within a surface grooveprovided in a spacer layer of the gasket, and adapted to be positionedat the edge of an engine combustion aperture.

FIG. 2 is an enlarged perspective break-away view of a portion of thegasket of the present invention to reveal details of a groove providedin the surface of an MLS cylinder head gasket spacer layer, showing theprotective metal tube positioned in the groove, wherein the top layer ofthe gasket has been cut back to reveal the tube.

FIG. 3 is a cross-sectional view of a portion of the protective tube,shown separately and apart from the gasket, displaying the end of thetube adapted to be positioned nearest the engine combustion aperture,corresponding to the view of FIG. 2.

FIG. 4 is a cross-sectional view of an intermediate portion of theprotective tube, also shown separately and apart from the gasket,displaying the pressure sensor apparatus contained within the metaltube.

FIG. 5 is a cross-sectional view of an end of the protective tubeopposite the end positioned near the engine combustion aperture,displaying features related to the protection of the sensor mechanism.

FIG. 6 is a cross-sectional view of the entire length of the protectivemetal tube, including all sections of the tube as displayed in FIGS. 3,4, and 5.

FIG. 7 is a cross-sectional view of an alternative embodiment of thegroove for positioning the sensor apparatus.

FIG. 8 is a cross-sectional view of another alternative embodiment ofthe groove formed in the spacer layer of the gasket.

FIGS. 9 a-9 d are alternative embodiments to achieve adequate sealing ofthe sensor tube adjacent to a combustion bore opening.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, one described embodiment of the pressuresensor apparatus of the present invention is herein described in detail.A combustion, or variously called cylinder head, gasket 10 is formed asa multiple layer steel (MLS) structure, and is of a type now commonlyemployed as combustion gaskets of internal combustion engines. Thegasket 10 is shown only fragmentarily, and includes a plurality ofcombustion apertures 12, of which only one is shown and describedherein. A plurality of bolt apertures 14, along with a plurality ofother apertures not identified, appear about the periphery of the gasketas shown. Finally, a plurality of grommets 16 are positioned so as tohold the plurality of metal layers together.

Referring now also to FIG. 2, the MLS gasket 10 includes at least a pairof layers 18 and 20. The top layer 18 is a beaded active layercontaining a metal bead 28, as will be appreciated by those skilled inthe art. Typically, the layer 18 has a counterpart mirror image layer(not shown) that defines a bottom layer, i.e. one positioned beneath thelayer 20, wherein the layer 20 acts as a non-beaded, non-active, spacerlayer.

A protective metal tube 22 lies in a groove 24 of the spacer layer 20 ina manner such that the groove 24 completely encases the metal tube 22,as shown. Alternatively, the grove 24 can be formed in both the spacerlayer 20 as well as in the upper layer 18. For example, referring toFIG. 7, instead of a single spacer layer 20 being provided with a singlegroove 24 deep enough for holding metal tube 22, spacer layer 20 issplit into two layers 20 a and 20 b that are positioned adjacent oneanother. Each of the layers 20 a and 20 b are provided with a groove 24a and 24 b wherein the depth of each groove is preferably at least abouthalf of the thickness of metal tube 22.

An end 26 of the tube 22 is positioned near the boundary of thecombustion aperture 12. To the extent that only one end 30 of anelongated gasket 10 is depicted (FIG. 1), references to apertures 12will be understood to extend beyond the single combustion aperture 12depicted in FIG. 1.

Referring now to FIGS. 3, 4, 5, and 6, the pressure sensor apparatus 60may specifically be described. Each of the FIGS. 3, 4, and 5, displaysonly a partial section of the tube 22, while FIG. 6 shows the entirelength of the protective metal tube 22. It will be apparent that thecombustion boundary end 26 of the metal tube 22, shown in most detail inFIG. 3, is the end protruding toward the combustion aperture 12 in FIG.2. On the other hand, an incoming fiber optic cable wire 34 is shown atthe extreme opposite end of the tube 22 in FIG. 5. Intermediatelypositioned between noted ends of the tube 22, FIG. 4 provides a detailedview of the sensor apparatus 60 that consists primarily of a silica tube50 which houses a strand of reflective fiber optic cable wire 36, spacedby a gap 38 from a reflective end 42 of the incoming fiber optic cablewire 34. The cable wire strand 36 and the reflective end 42 are fusedvia high temperatures to the internal diameter of the silica tube 50 soas to fix the gap 38. The respective spaced parallel ends 52 and 54 ofthe latter members are squared with respect to one another, as shown, soas to enable changes in intensity of light emitted through the incomingcable wire 34 to be measured with great accuracy.

Referring specifically now to FIG. 3, an interior bore 32 of thecombustion end 26 of the tube 22 is adapted for receiving a metallicpressure diaphragm 40, similar to an end cap, by which combustionpressure may be received and transmitted through a fluid medium, such asa column of oil 48, to the sensor apparatus 60. In the describedembodiment, the diaphragm is manufactured of nickel alloy metal toprovide appropriate characteristics of heat resistance and pressuretransmission for the intended environment. Due to the miniature size ofthe pressure diaphragm 40, the diaphragm is also referred to as amicro-bellows mechanism. For example, FIG. 9 a shows an enlarged view oftube 24 that is provided with a diaphragm 40 at combustion end 26.Diaphragm 40 fits within a chamber 39 formed located adjacent tocombustion opening 12. Alternatively, diaphragm 40 may be press fit intogroove 24 and onto end of tube 22 to properly seal metal tube 22 againstthe wall 41 of combustion aperture 12.

Referring to FIG. 9 b, in an alternative embodiment to use of diaphragm40, tube 24 may be provided with a trumpet type distal end 43. In thisembodiment, trumpet type distal end 43 engages the wall 41 of combustionaperture 12. Ideally, distal end 41 is sized so as to be slightly largerthan the diameter of groove 24 so as to seal around groove 24.

In yet another alternative embodiment, referring now to FIG. 9 c, aportion of groove 24 is proved with a plurality of “teeth” 45 or threadsto provide localized contact pressure and create several pressurebarriers around tube 22. The teeth 45 are positioned adjacent to thecombustion aperture 12.

In yet another alternative embodiment, referring now to FIG. 9 d, an endportion 47 of tube 22 may provided with triangular shape such that edges49 a and 49 b extend away from one another. In accordance with thisaspect of the invention, end portion 47 is press fit into groove 24,thereby sealing tube 22 within groove 24.

Referring now to FIG. 5, it will be noted that downstream of the sensorapparatus 60 is positioned a so-called wick stop material 44 installedduring manufacture to arrest wicking of any high temperature adhesivematerial 46 into the oil entrained portion of the tube 22. Thusreferring specifically to FIG. 6, it will be noted that theoil-entrained columns 48 are both upstream and downstream of the sensorapparatus 60. Those skilled in the art will appreciate that the hightemperature oil 48 must be of a type not subject to significant thermalexpansion. One such as choice is a so-called diffusion pump type of oil.Another is a silicone brake fluid such as that used in automotive brakesystems, and subject to temperatures of up to at least 400 degreesFahrenheit. The wick stop material 44 in the described embodiment is ofa high temperature RTV elastomer, and is used because the hightemperature adhesive material 46 is applied in a fluid state during themanufacturing process.

Referring now to FIGS. 4 and 6, it will be appreciated that the sensorapparatus 60 incorporates a silica tube 50 that floats in the oil column48 within an intermediate portion of the tube 22. In the describedembodiment, there is no adhesion or attachment in the interface 56 (FIG.4) between the silica tube 50 and the metal protective tube 22. Themetal protective tube 22 is thus free to expand and contract in theengine environment relative to the apparatus 60.

Finally, those skilled in the art will appreciate that the opticalsignals generated by means of the sensor apparatus 60 are created byvirtue of fluctuating changes in the gap 38 caused by responses of thepressure diaphragm 40 to combustion activity occurring within thecylinders 12. As appreciated by one skilled in the art, changes inpressure adjust the overall axial length of the silica tube 50, therebychanging the distance of the gap 38 between the cable wire strand 36 andthe reflective end 42 of the incoming fiber optic cable wire 34. Suchsignals must ultimately however be converted into electrical signals forpurposes of being read appropriately by an engine control module 62(FIG. 6) for providing real-time engine management, includingoptimization of fuel economy and emissions levels.

The process for manufacturing a spacer layer 20 having at least onegroove 24 will be discussed. First, groove 24 is rough cut into spacerlayer 20. If groove 24 is only formed in a single spacer layer 20, thenat least one surface 61 of spacer layer 20 is preferably provided with athin support layer 63, as shown in FIG. 8. Thin support layer 63 may beattached to spacer layer 20 by spot welding or other suitable method.Once the rough cut groove 24 is formed, final shaping must be performed.Final shaping may be accomplished by either milling, saw blading a path,beading, or coining to the final shape.

It is desirable that an adequate seal is provided between the wall ofgroove 24 and an outer surface of tube 22. Even if the tolerances aretightly controlled between metal tube 2 and the groove wall 24,microsealing is desired. There are several different methods that aredesirable to provide the sealant coating in groove 24. One methodincludes applying sealant coating to a flat layer before the groove isformed. However, use of this method requires that groove 24 must beformed through use of a forming process as opposed to a machiningprocess. Alternatively, the sealant coating may be applied after thegroove 24 is formed, through use of a screen printing process.

In another alternative embodiment, the sealant coating may be applieddirectly to metal tube 22 prior to insertion of metal tube 22 intogroove 24. Due to the conformability of the sealant coating, once metaltube 22 is placed in groove 24, the coating will seal any gap betweenthe wall of the groove 24 and metal tube 22. Many different types ofcoatings may be employed to affect the sealing between the groove 24 andthe metal tube 22. Suitable coatings include FKM based coatings,thermoplastic, cement (must be applied in a fluid stage and cured aftersensor is assembled) and foam-like coatings.

It is to be understood that the above description is intended to beillustrative and not limiting. Many embodiments will be apparent tothose of skill in the art upon reading the above description. Forexample, a gasket within the sensor elements and wires molded into thebody of the gasket material would fall within the broader scope of thisinvention. Therefore, the scope of the invention should be determined,not with reference to the above description, but instead with referenceto the appended claims, along with the full scope of equivalents towhich such claims are entitled.

1. A combustion pressure sensor in a cylinder head gasket adapted foruse in an internal combustion engine, the gasket defining at least onecombustion cylinder bore aperture, the sensor adapted for placement at aboundary of the bore aperture; wherein the sensor is adapted to measurecombustion pressure changes within a cylinder bore of the engine fordetermining engine conditions including predetonation, said sensor andsaid gasket, comprising: a groove located within said gasket, saidgroove at least partially extending through said gasket at a firstdiameter, wherein said groove diameter increases to a second diameteradjacent said at least one combustion cylinder bore aperture to define achamber; and a diaphragm having a inner first portion connected to atube within said first diameter portion of said groove, and an outersecond portion that is connected to said inner first portion, whereinsaid outer second portion has a larger diameter than said first diameterof said groove, said outer second portion being entirely housed withinsaid chamber.
 2. The combustion pressure sensor and gasket of claim 1,wherein said diaphragm inner first portion has an outer diameter greaterthan an outer diameter of said tube.
 3. The combustion pressure sensorand gasket of claim 1, wherein said diaphragm has a complementary shapeto said chamber.
 4. A combustion pressure sensor and gasket adapted foruse in an internal combustion engine, the gasket defining at least onecombustion cylinder bore aperture, the sensor adapted for placement at aboundary of the bore aperture; wherein the sensor is adapted to measurecombustion pressure changes within a cylinder bore of the engine fordetermining engine conditions including predetonation, said sensor andsaid gasket, comprising: a groove located within said gasket and a tubelocated within said groove, said groove comprising a plurality ofinwardly extending, circumferential teeth located within said grooveadjacent said combustion cylinder bore aperture and in contact with saidtube.
 5. The combustion pressure sensor and gasket of claim 4, whereinsaid teeth are integrally formed and one-piece with said groove.
 6. Thecombustion pressure sensor and gasket of claim 4, wherein said teeth arethreads.
 7. The combustion pressure sensor and gasket of claim 4,wherein said plurality of teeth create several pressure barriers aboutsaid tube.
 8. A combustion pressure sensor and gasket adapted for use inan internal conbustion engine, the gasket defining at least onecombustion cylinder bore bore aperture, the sensor adapted for placementat a boundry of the bore aperture; wherein the sensor is adapted tomeasure combustion pressure changes within a cylinder bore of the enginefor determinig engine conditions including predetonation, said sensorand said gasket, comprising: a groove located within said gasket andtube located within said groove, wherein a portion of said tube locatedadjacent said combustion cylinder bore aperture has laterally opposededges that extend away from one another.
 9. The combustion pressuressensor and gasket of claim 8, wherein said portion of said tube ispress-fit into said groove to seal said tube within said groove.
 10. Thecombustion pressure sensor and gasket of claim 8, wherein said portionof said tube has a generally outwardly extending triangular shape.
 11. Acombustion pressure sensor in a cylinder head gasket adapted for use inan internal combustion engine, the gasket defining at least onecombustion cylinder bore aperture, the sensor adapted for placement at aboundary of the bore aperture; wherein the sensor is adapted to measurecombustion pressure changes within a cylinder bore of the engine fordetermining engine conditions including predetonation, said sensor andsaid gasket comprising: a groove extending through said gasket at afirst diameter, said groove extending to an opening in said combustioncylinder bore aperture, said gasket defining a circumferential wallabout said opening; and a tube extending through said groove and atleast partially into said combustion cylinder bore aperture, said tubehaving an integrally formed curvilinear distal end positioned about saidcircumferential wall.
 12. The combustion pressure sensor and gasket ofclaim 11, wherein said distal end is a flared trumpet-type distal end.13. The combustion pressure sensor and gasket of claim 12, wherein saidwall about said opening is larger than the flared distal end of saidtube.